PROJECT SUMMARY Cancer is the second leading cause of death in the United States, accounting for approximately 25% of deaths. The national medical expenditures of cancer reached $125 billion in 2010, and are projected to increase to $158 billion by 2020. A recent Institute of Medicine report, entitled ?Delivering high-quality cancer care: Charting a new course for a system in crisis,? expressed major concerns over the unsustainable increase in the cost of cancer care, identifying rapid diffusion of new technologies and the aging demographic as key cost drivers. The objective of the proposed study is to examine the impact of technology diffusion in medical, radiation, and surgical oncology on the costs and outcomes of cancer care. Specific aims of the study are: (1) to describe the pattern of technology diffusion in medical, radiation, and surgical oncology in the top five most expensive cancers and assess the geographic variation of the diffusion pattern; (2) to examine factors associated with the diffusion of new technologies and those that contribute to the geographic variations in new technology diffusion; (3) to evaluate the impact of the diffusion of new oncologic technologies on health outcomes and whether the impact would be modified by guideline adherence; and (4) to estimate the effect of the diffusion of new oncologic technologies on the cost of cancer care and geographic variation in healthcare spending, and to explore for each cancer whether these new technologies are substitute or complementary to existing treatment. We will address our research questions using a cohort of cancer patients extracted from the SEER-Medicare and MarketScan? databases, focusing on the top five most expensive cancers: female breast, colorectal, lymphoma, lung, and prostate cancer. Our study will provide a comprehensive evaluation of the current state of technology diffusion for all modalities involved in the treatment of cancer, paying special attention to market and organizational characteristics tied to providers? financial incentives. The choice of cancer to study technology diffusion offers a unique opportunity to understand the complicated interactions between new and existing technologies and allows us to explore the substitution or complementary effect of new technologies, both within the same class of technology and across classes. Findings from our study will assist policy makers in the design and planning dissemination and implementation strategies to maximize the benefit of effective new treatments while taking into consideration of the cost implications to the cancer care delivery system.